JPH0215863A - Pressurized casting method - Google Patents

Abstract

PURPOSE:To accurately execute squeeze pressurization and to surely prevent the development of shrinkage hole by beforehand projecting a pressurizing plunger into cavity in a die, filling up molten metal to retreat the pressurizing plunger and advancing the pressurizing plunger after passing the prescribed time to execute the pressurization. CONSTITUTION:Before filling up the molten metal 8 into the cavity 6 in the mold 1, beforehand the pressurizing plunger 13 is projected into the cavity 6 at few mm, and both chambers 12A, 12B of a pressurizing cylinder 12 are kept to condition of introducing into an oil reserve tank. Successively, by advancing the injecting plunger 10, the molten metal 8 in a sleeve 7 is filled up into the cavity 6 and the pressurizing plunger 13 is retreated to the reference point. After passing the prescribed time since retreating the pressurizing plunger 13, the pressurizing plunger 13 is gradually advanced into the cavity 6 filling up the molten metal 8 to the prescribed stroke, to execute the squeeze pressurization. By this method, the molten metal 8 in the cavity 6 is surely fed, to surely prevent the shrinkage hole.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a casting method in which molten metal is injected into a mold cavity to form a mold, and particularly relates to a pressurizing method that improves the process of pressurizing the molten metal in a mold. This relates to a casting method.

[Prior Art] An example of a conventional mold casting method will be described with reference to FIG. 2.

In FIG. 2, the mold 1 is composed of a fixed mold 2 and a movable mold 3, and the fixed mold 2 and the movable mold 3 each have a fixed platen 4.
and is attached to the movable platen 5. These fixed mold 2 and movable mold 3 are clamped by a mold clamping mechanism (not shown),
The molten metal 8 in the sleeve 7 is injected into the cavity 6 thus formed by the injection plunger 10 of the injection device 9, solidified and molded under pressure by the injection plunger 10. Note that FIG. 2 shows a state in which the cavity 6 has already been filled with the molten metal 8.

Depending on the shape of the molded product (cast product), it may not be possible to prevent sink cavities that occur during solidification of the molten metal by applying pressure using the injection plunger 10 alone. Therefore, as shown in FIG. 2, the pressurizing cylinder 12 of the pressurizing device 11 is operated to advance the pressurizing plunger 13, and the injection plunger 10
The molten metal 8 is pressurized at a pressure greater than the pressure applied to the molten metal 8 by the molten metal 8. This pressurizing device 11
This pressurization is commonly called squeeze pressurization. In addition, in FIG. 2, the pressurizing cylinder 12 has hydraulic pipes 14 and 15.
The pipes 14 and 15 are connected to valves 16 for switching the direction of hydraulic pressure flowing from a hydraulic source (not shown).

FIG. 3 shows the overall operating sequence of the mold casting method in which squeeze pressure is applied and the pressure changes within the mold during this casting process. As shown in FIG. 3, the pressurizing cylinder 12 is operated when a predetermined pressurizing time lag Δ has elapsed from the completion of filling with the injection plunger 10, and the pressurizing plunger 1
3 to press the molten metal 8 and apply a predetermined squeeze pressure pso. Note that the filling of the molten metal 8 into the cavity 6 by the injection plunger 10 is normally completed by the injection plunger 1.
This is often the point at which the operating pressure of the injection cylinder (not shown) that presses 0 suddenly changes.

[Problems to be solved by the invention] When the shape of the molded product is complex or when filling the molten metal at a very low speed to prevent the entrainment of cloudy air inside the cavity, it is necessary to At the time when the operating pressure of the cylinder suddenly changes), the cavity 6 may not yet be filled with the molten metal 8 as shown in FIG. This is because: ■ When filling the molten metal at a low speed, the viscosity of the molten metal may increase at the end of the cavity; ■ Depending on the mold, there may be a constricted part as shown in Figure 4 A, for example. However, since the flow resistance of the molten metal is quite large in this constricted portion A, the pressure applied to the molten metal by the injection plunger is supported to some extent. Therefore, the time when the cavity 6 was actually completely filled with the molten metal 8 could be several seconds after the point of sudden change in the operating pressure of the injection cylinder.

Therefore, in the conventional squeeze pressurization method, the pressurizing plunger 1 is in a full state where the cavity B remains as shown in FIG.
There were times when I ended up moving 3 forward. In such a case,
The pressurizing plunger 13 only fills the void B, and does not provide the squeezing effect of pressurizing the molten metal. Moreover, depending on the temperature state of the mold 1, the flow resistance of the molten metal introduced into the constriction A in FIG. Since the time also varies greatly, it is not possible to accurately predict the pressurization time in advance and always perform squeeze pressurization at an appropriate timing.

Moreover, for this reason, conventionally the pressurization time lag Δ
To adjust t, a worker observes the cast product to judge whether it is good or bad, and then frequently adjusts Δt, which makes the molding work time-consuming and requires a skilled worker. In addition, there were problems such as a tendency for loss to occur in the molded product.

[Means for Solving the Problems] The pressure casting method of the present invention includes filling a mold with molten metal using an injection device and pressurizing the molten metal in the mold using a pressurizing device having a pressure plunger. In the method, a pressurizing plunger is projected into the mold cavity by a predetermined amount before filling the mold cavity with molten metal, and it is detected that the pressurizing plunger is retracted when the filling of the mold cavity with the molten metal is completed. However, this retreat is set as a reference point for starting the operation of the pressurizing plunger, and after a predetermined time has elapsed from this reference point, the pressurizing plunger is advanced into the mold cavity to start pressurizing the molten metal.

[Operation] In the method of the present invention, the time when the pressure plunger is pushed back is the time when the molten metal actually reaches the tip of the pressure plunger. Therefore, when the pressurizing plunger is advanced after a predetermined period of time has elapsed since the pressurizing plunger was pushed back, the mold cavity is reliably filled with molten metal, and the molten metal is accurately pressed. It can give a hot water effect.

[Example] Examples will be described below with reference to the drawings.

FIG. 5 is a sectional view of a main part of a pressure casting apparatus suitable for carrying out the method of the present invention. In FIG. 5, pressurizing plunger 1
In order to detect the moving stroke amount of No. 3, a direct-acting position detector 21 is provided.

In this embodiment, this position detector is a variable resistor, which divides the voltage of the power supply 22 proportionally depending on the position of the pressurizing plunger 13, measures the divided voltage with the voltage measuring device 23, and calculates the value externally. It is configured to output to the control device 24.

This external control device 24 connects the valve 1 for hydraulic control.
A control signal is output to 6. The rest of the configuration in FIG. 5 is the same as that in FIG. 2, so the same members are given the same reference numerals and their explanations will be omitted.

In this embodiment, the pressurizing plunger 13 is moved back and forth by controlling the valve 16 as follows.

First, in FIG. 5, before the injection plunger 10 fills the molten metal 8 into the cavity 6, for example, the sleeve 7 is filled with the injection plunger 10.
When the molten metal 8 starts to be absorbed, the solenoid a of the valve 16 is turned on, and the head end side 12 of the pressurizing cylinder 12 is turned on.
Hydraulic pressure is introduced into A and the pressurizing plunger 13 is made to protrude into the cavity 6 by several mm (for example, 3 to 5 mm). The output of the position detector 21 at this point is the initial setting value when 1=0 shown in FIG. Note that in FIG. 1, the stroke amount O is at the time when the pressurizing plunger 13 is most retracted.

After advancing the pressurizing plunger 13 by the initial setting value as described above, the valve 16 is set to neutral, thereby allowing the two chambers 12A, 12 separated by the piston 12a of the pressurizing cylinder 12 to
Both B and B are electrically connected to the oil reservoir tank (see Figure 6).

After the sleeve 7 has received the molten metal 8, the injection cylinder (
(not shown) to advance the injection plunger 10,
The cavity 6 is filled with molten metal 8. When the cavity 6 is filled with the molten metal 8, the piston 12a of the pressurizing cylinder 12 is in a state where it can move freely back and forth, so the pressurizing plunger 13 is pushed back by the molten metal 8 as shown in FIG. Note that FIG. 7 shows a state in which the pressurizing plunger 13 has begun to be pushed back.

In this embodiment, as shown in FIG. 8, the reference point is the point when the pressurizing plunger 13 is retracted the most and its stroke amount becomes 0. Then, from this reference point, the pressurization time lag Δ
After passing through, the solenoid a of the valve 16 is actuated to introduce hydraulic pressure to the head end side 12A of the pressurizing cylinder 2, and the pressurizing plunger 13 is pushed into the cavity 6 filled with molten metal as shown in Fig. 9. Start squeezing pressure. Thereafter, as in the conventional case, the pressurizing plunger is gradually advanced to a predetermined stroke amount.

Then, the molten metal is solidified, and then hydraulic pressure is introduced into the rod end side 12B of the pressurizing cylinder 12, and the pressurizing plunger 1
After retracting step 3, the mold is opened and demolded.

By starting the squeeze pressurization operation in this way, the squeeze pressurization can be performed accurately and the feeder effect can be reliably applied to the molten metal 8 in the cavity 6.

In the above embodiment, a configuration using a variable resistor is used as the position detector 21, but it is clear that position detectors with various configurations other than this can be used.

Further, the present invention is not limited to the shape of the mold and the configuration of the pressurizing device 11 and the like to those shown in the drawings, and various types of devices that can perform the above operations can be adopted. Furthermore, it is clear that the pressurizing devices may be provided at two or more locations for one mold. The present invention is particularly suitable for application in a case where the pressurizing device is placed apart from the injection device as shown in the drawings.

[Effects] As described above, according to the pressure casting method of the present invention, the molten metal in the cavity can be reliably fed. Therefore, it is possible to reliably prevent sinkholes, and it is possible to reliably cast high-quality molded products. Further, the adjustment work of the pressurization time lag Δt, which was conventionally frequently performed by workers, is no longer necessary, no skilled workers are required, and the casting time cycle is significantly shortened. Therefore, according to the present invention, the production efficiency of the pressure casting apparatus is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of a pressure plunger showing the pressure casting method of the present invention, FIG. 2 is a sectional view of a conventional pressure casting apparatus M, and FIG. 3 is a graph explaining the conventional squeeze pressurization method. FIG. 4 is a sectional view of the main part of a mold during pressure casting by the conventional method, FIG. 5 is a sectional view of the main part of an apparatus suitable for carrying out the method of the present invention, and FIGS. FIG. 9 and FIG. 9 are sectional views of essential parts of a casting apparatus for explaining an embodiment method of the present invention. 1... Mold, 6... Cavity, 8... Molten metal, 10... Injection plunger, 11...
Pressurizing device, 12... Pressurizing cylinder, 13... Pressurizing plunger, 16... Hydraulic valve. Patent Applicant Ube Industries Co., Ltd. Representative Patent Attorney Tsuyoshi Shigeno Figure 2 Figure 1 ↑ ↑ Squeeze pressurization begins J seat crowd - Figure 4 Figure 6 Figure 7 Figure 5 Figure 8 Figure 9

Claims (1)

[Claims] (1) In a pressure casting method in which the mold is filled with molten metal using an injection device and the molten metal in the mold is pressurized using a pressurizing device having a pressure plunger, before filling the mold cavity with the molten metal. A pressurizing plunger is made to protrude into the mold cavity by a predetermined amount, and when the filling of the molten metal into the mold cavity is completed, it is detected that the pressurizing plunger is retracted, and the operation of the pressurizing plunger is started at the time of retraction. A pressure casting method characterized in that a reference point is set, and after a predetermined period of time has elapsed from this reference point, a pressure plunger is advanced into a mold cavity to start pressurizing the molten metal.